Applicants' invention relates generally to radiocommunication systems, e.g., cellular or satellite systems and, more particularly, to techniques for supporting and enhancing emergency calling procedures in such systems.
The growth of commercial radiocommunications and, in particular, the explosive growth of cellular radiotelephone systems have changed the ways in which people communicate. One survey indicates that about 80% of the people who purchase mobile communication units and service subscriptions do so to enhance their personal security. Presumably, many of these subscribers would expect to use their mobile units to aid them in urgent situations, e.g., when their vehicle has become disabled or in an emergency situation requiring rapid medical and/or police response. However, it may be desirable to process emergency calls differently from non-emergency calls. For example, it may be desirable that access to the radiocommunication system be as fast as possible so that an emergency service center can respond quickly to the user's request for assistance or that the emergency service center be provided with location information which pinpoints the position of the emergency caller.
To aid in adjusting the processing of emergency calls, it may be useful that the mobile unit be able to recognize when a user is placing an emergency call so that the mobile unit can modify its normal call processing procedures. Examples of ways in which the mobile station might adjust its normal call processing procedures when it recognizes that an emergency call has been placed are described in U.S. patent application Ser. Nos. 08/839,859 (Attorney Docket No. 027575-062) and 08/843,752 (Attorney Docket No. 027575-063), entitled "Systems and Methods for Handling Emergency Calls in Hierarchical Cell Structures" and "Systems and Methods for Increasing Emergency Call Access Speed in Radiocommunication Systems", respectively, both of which were filed on Apr. 22, 1997. Of course those skilled in the art will appreciate that other mobile unit call processing routines could also be adjusted to optimize emergency call handling once the placement of such a call has been recognized.
Moreover, some systems provide mechanisms for the mobile unit to alert the system of a request for emergency access independent of the dialed number. For example, systems defined by IS-136 provide a field in the Origination Message wherein a bit flag can be set when the mobile station recognizes that an emergency access has been requested.